This invention relates to hydraulic control systems and more particularly to hydraulic control systems for hydraulic retarders.
Prior art retarder controls generally provide some means, such as an accumulator, for assisting the control pump in supplying fluid to the retarder at initiation. These systems have a high pressure discharge at the retarder outlet which is directed through a cooler and back to the retarder inlet to mix with retarder inlet flow from the pump. This reduces the pump requirement but retarder charge pressure and thus torque capacity is limited by the design strength of the cooler.
Other devices utilize an output driven pump, the main function of which is to supply the retarder with pressurized fluid. These systems also utilize flow recirculation so that the output pump flow requirements can be maintained at a minimum value. Therefore, these systems also limit retarder charge pressure to cooler pressure capacity.